Signaling system



Jan. 8, 1946, G. L. ussELMAN SIGNALING SYSTEM Filed Sept. 9, 1943 Patented Jan. 8, 1946 SIGNALTNG SYSTEM- George L. Usselman, Port Jefferson. N. Y., assignor to Radio Corporation of America, a. corporatio'n of Delaware Application September 9, 1943, Serial No. 501,647

4 Claims.

In signaling systems comprising a wave source and wave modulating tubes associated therewith, it is desirable to have a constant voltage source of direct current supply in order thatdistortion of the.modulated wave is not caused during operation due to poor voltage regulation.

In systems as described above, for operation on telephony or telegraphy signals the modulation tube load and operation is different for the two types ofsignals and the drain on'the direct current source is different in each case, thereby in creasing the need of a compensated or regulated source in order that distortion does not result due to poor regulation.

In systems where the wave source is to be modv ulated as to timing in accordance with telephony or telegraphy signals and the modulating tube or tubes are simulated reactances controlledin accordancewith the signals by'controlling the current therethrough distortion as such results from poor regulation in the direct current supply source, and -in addition considerable undesired amplitude modulation may be caused along with the desired timing modulation.

The general object of my invention is improvedoperation of telephonycr telegraphy systems using an unregulated or poorly regulated direct current supply source.

This general object is attained by loading the source with a thermionic load that is o f different value for the two types of signals and varying the load as the signals vary in a direction to compensate changes in the load placed on the source by the modulator and wave source as modulation is carried out. By the expression modulation here is meant control by code or voice or similar signals.

Other objects. and the manner in which the same are attained, and the advantages which fiow acter of the wave through a modulator tube or tubes.

In the drawing V1 is an oscillation generator of the regenerative type having its cathode and grids G1 and G2, the latter' acting as an anode, connected in a grounded anode Hartley type oscillator. The anode I0 is coupled to an output circuit not shown and coupled to the generation electrodes and circuit by the electron stream in the tube. The condenser Coimproves the generator operation..

The -generated oscillations produce a voltage drop`across the resistance R1, which is also a leak resistance for the grid G1, and from this resistance R1 voltage of the generated frequency is fed'by condenser 26 to the grid 24 of the modulator tube V2. The anode 40 of modulator tube V2 amplies this voltage and the sameis set up in circuit L2, Ca, C4 and fed by crystal 5 to the grid G1.

The phase ofthe voltage at 24, is say the same as at G1 and the voltage is reversed by tube V2. The tank circuit L2, Ca is detuned slightly to further shift the phase of the amplified voltage about 90 plus or minus so that on the grid G1 is developed a Voltage that is the resultant of the two voltages, i. e., the generated voltage and the amplifled voltageA fed back by V2 which at no modufrom the use of my invention will appear from the detailed description which follows. In this de scription reference will be made to the attached drawing in which the single iigure illustrates one embodiment .of a signaling system arranged in a'ccordance with my invention.

In describing my improved means, I have shown the same incorporated in signaling systems as disclosed in my United States Patents No. 2,298,436, No. 2,298,437 and No. 2,298,438, all dated November 13, 1942. It4 will be understood, however, that the improvements apply equally well to signaling systems of other types'v wherein a wave source,

which may be a tube lgenerator or ampliiier, is

modulated by code or voice acting on the charlation are about 90? displaced in phase.

Tube V2 has its grid 24 'modulated through resistance R2 by code from source 50 when switch Ms is at the right or by voice from transformer y T when the switch MS is at the left. This modulates the amplitude of one of the phase displaced voltages fed to the grid G1 and as a consequence modulates the phase of the resultant voltage on G1 in accordance with signals. The voltage then fed back to vgrid 24 of tube V2 is correspondingly shifted in phase and the effect is accumulative so that the generated oscillations are modulated in frequency in accordance with signals.

It'is .believed that the brief description given A above is sucient, since the operation of this part of the system is known in the art, having been described in detail in my United States patents mentioned above. Attention isv directed to Fig, 4 of Patent No. 2,298,437.

The direct current source 616 has a negative terminal grounded, being thereby connected to the cathodes of tubes V1 and V2,-and has its positive terminal coupled to the screen grids and anodes of tubes V1 and V2 to supply direct current operating voltages. The current in tube V2 is controlled. for signaling purposes as described above and this places on supply source a varinais To insure a constant voltage at the source tl which may bean unregulated supply source,

I provide two compensation tubes V: and V4. These two tubes have their cathodes 82 and 6l tied together and. connected to ground through the cathode resistor $6 shunted by bypassing condenser -68. The switch 89 when in the left hand position connects thecathodes B2 and 6d directly to ground, thus shunting resistance te. The control grids 10 and 'i2 or the tubes Va and Ve are connected by resistances Re and Re c.

to the switch MS and by said switch in the left hand position through the secondary winding of n'ansformer T and bias source 'Iii to ground. When the switch MS is at the right these grillsi are connected by the bias source iS to ground. j

The anode Bil and screen grid of tube Vs is connected by resistance 82 and switch 69 in the left hand position to source B6. The anode 84 and screen grid of-tube V4 is connected by resistance 8'@ to the source 80.

When voice or similar modulation is to be used the switch MS is closed in the position shown as is the switch te. The resistance 6 8 is thereby short-circuited and lthe cathodes of tubes V2, V: and V4 are connected directly to ground.

The grids l@ and 12 of tubes Vs and V4 are now connected by switch MS to one end o f the secondary winding of transformer T, While the grid 24 of tube Vn is connected to the other end of this winding. The anode circuit of tube Vs' is interrupted by switch 89 and thus the tube V4 vthe anode St' 'of whichis connected to source to serves to load the said source differentially with respect to the loading thereof during operation-by the modulator tube Vn. The connec- 4o l. In apparatus of the class described, a source tions including the bias resistance Re are such .that a substantially constant drain and load is placed onsource ,80. During modulation tubes V4 and Vc are modulated by transformer Tin phase opposition, that is in pushpull relation, so that when anode current increases in tube Vn it decreases a like amount in tube V4 and vice versa, thereby maintaining a constant load current and consequently constant-load voltase is maintained. i

In the code or telegraphy position switch MS is 'moved to the right ena switch sa' is moved to the left. (The `showing is schematic and these switches in practice may be arranged lor common control as' desired.) This removes the short circuit across resistance l! and the cathodes of tubes V2, V3 and V4 are biased positive with respect to ground by current through resistance cl. The anodes 'oi' both tubes Va and V4 arenow 'V eonoeeted to the source n by ewiton sa end the g A is increased. This increases the negative bias on thesrids'll and I2 ofthe compensator tubes va and V4, since their normal fixed control grid f bias from' source 'Il is unchanged, therebyreducing the anode currentinthe-compensator tubes! by almost the same amount that'the current to the teodoro: tube ve me been increased.

the snode current in the modulator tute ve lo by keying-its grid more. trentini 'I through tube ve.

@scacco the drop through resistance decreases, the potential on the grids 'l0 and 120i' tubes V3 and V4 becomes less negative and these tubes take more c current to compensate the decrease in current Consequently, substantially constant rectiiler (in say 60) load current and voltage is maintained without additional power supply regulation. I

The grid bias on tubes Vz, Vs and V4 is not lnecessarily higher in the telegraph position as compared to the phone position although the cathode bias may be higher, The grid bias on these tubes can be made to have any desired value by adjustments' of the bias sources it, 18,

lo and lo. The purpose of cathode resistor Se is for a differential biasing means (opposite biasing means) for tubes Va and Vt when tube V2 is keyed 'by ltelegraph signals. The cathode resistor 61S is not needed for compensation in the telephone 2o position. In fact, yits use in this latter case causes distortion oi the signal and sometimes undesirable uncontrolled oscillations in these circuits.

Hence the switch |59 for shorting resistor 6B in the phone position. It might be stated here that 25 bias sources N, mand 'i8 are actually obtained lect compensation, thatv is, constant voltage at l the source' and on the .tube electrodes. In. the telegraph setting two compensator tubes gives better 'compensation than one tube. Perfect compensation in the telegraphsetting is not feasible by this method but also perfect compensation for the telegraphy setting is not necessary. However,

the compensation obtained in my system is satisfactory.

I claim: p

of direct current potential, a tube having electrodes in a direct current -circuit including said source as a supply of operating potential, connec- -tions for controlling the current through said tube in accordance with telephony signals or code 4signals whereby said source vis vloaded variably during operation, a pair of compensating tubes each having output electrodes, a direct current circuit including said source for the output elec- 0 trodes of one of said pair of tubes when telephony is used and both of said pair of tubes when code is used and connections for controlling the current through said one of said pair of tubes in a sense opposite to control of the current through 55. said rst tube by telephony and connections for controlling the current through both of said pair of tubes in a sense opposite to the control .of the current through said first tube by code.

2. Inapparatus of the class described, a modul lator tube artangedto modulate wave energy. Iin

accordance with telephony-or code signals, said modulator tube having electrodes including. -a

cathode and an anode. a source of direct current in a direct current circuit for said cathode and anode. a pair of compensating tubes each having control o! said ilrst tube by telephony signals, 7 connections between the output electrodes of said one oi' said compensating tubes and said source tot direct currentconnections for controlling thevcurrent through both of said compensating tubes in phase' opposition with respect to .the control I 1310! I dd ont tuberi code. aus wouectlout.te-l

tween the output electrodes of both compensat ing tubes and said source of direct current.

3.- In a signaling system, a modulator tube havv ing electrodes including an anode and cathode, a source oi direct current having a positive terminal connected to said anode and a negative terminal grounded, a bias resistance connecting the cathode oi said tube to ground, a source of telephony signals, a source of telegraphy signals, connections including a switch connecting one or" the other of said signal sources to an electrode of l sistance and connecting an electrode in each of said compensating tubes to said source of telegraphy signals when the same is connected to said one electrode in said modulator tube.

4. In'a signaling system, a source of direct current potential, a tube having electrodes in a di-` rect current circuit including said source as a supply of operating potential, connections for controlling the current through said tube in accordance with telephony signals or code signals whereby said source is loaded variably during operation, a pluralityv ofl discharge devicesveach having electrodes, a direct current circuit, including said source,'for the electrodes of at least one of said devices when telephony is used and for' at least two of said devices when code is used and connections for controlling the lcurrent through said one of said devices in a sense oppo- -site to control of the current through said rst tube by telephony and connections for controlling the current through said two of said devices in a sense opposite to the control of the current throughsaid iirst tube by code.

GEORGE L. USSELMAN. 

